Generally rope winding systems are well known which use various techniques or constructions in order to apply a more or less constant load to a steel rope while it is wound onto a rope drum of a rope winch, in particular of a crane, so that the steel rope can be uniformly wound onto the rope drum in several layers.
For example, pressure rollers are used in order to avoid slack rope problems in spooling operations. The pressure rollers used do not, however, always contact the entire width of the rope drum, so that the pressure roller experiences different loads as the rope is wound up. The use of pressure rollers results in high wear and tear of the steel rope. Also, pressure rollers tend to skip, which may lead to damage. The skipping may be due, for example, to the rope drum not being entirely uniformly wound. Such a design is sold, for example, by the firm Rotzler (Germany).
In another approach to solve the problem of winding up or down a steel rope, outer and inner rope drums are provided, as disclosed in DE 43 16120 A1. A continuous rope can be wound onto a storing drum and a working drum wherein the working drum surrounds the storing drum and is concentrically mounted to the latter on the drum shaft. The drum housing of the working drum is provided with an axially extending gap for passing the rope, and the working drum is freely rotatable on the drum shaft. A clutch for the non-rotating coupling of the working drum to the storing drum is also provided. In this arrangement, the rope length not needed for a particular operating mode is stored on the storing drum. During operation, the rope on the working drum is almost entirely wound and unwound. This makes it possible to avoid winding up the rope while a load is applied onto layers of windings that have become loose. The rope can be loosely wound onto the inner storing drum at each required rope length, as it is only stored thereon. This construction is, however, very complex and only results in transferring the rope to the inner drum. No load is built up on the rope and only unused lengths of rope are transferred.
From DE 199 03 094, two rope drums arranged side by side, are known. Herein, a hoist rope drum and a storing drum are fixedly linked coaxially with each other and axially offset from each other, and are driven by a common drive motor. Both the hoist line drum and the storing drum are always commonly driven, wherein the hoist line section stored on the storing drum is not loaded.
A line haul for steel cable including one or more power sheaves ahead of a cable storage drum is shown in U.S. Pat. No. 3,512,757. Each sheave has as circumferential groove in which the cable fits closely and unlike magnet poles are spaced transversely of the groove to produce a flux path intersecting the groove transversely of its length and pathing through the cable transversely of its length. The principle object of such an arrangement is to increase the traction between a cable bight and the groove of a sheave in which such cable bight is received without reliance primarily on the force of friction between the cable and the surface of the sheave groove.
From GB 820,051 A, a capstan device for use in hauling steel cable is known. It is emphasized that it would be important to know precisely the length of a cable passing over the device and to ensure that the cable is not damaged in the process. Difficulty has arisen in the past since there is almost inevitably appreciable slip. The device shown in GB 820,051 A comprises means disposed within a cable-engaging member to provide a magnetic field having a component normal to the external surface and thus tending to retain the cable in contact with that surface.
In GB 1,152,410 A an overhead traveling crane or lift driven by a linear induction motor is shown, in which a laminated moving member totally surrounds a portion of a length of a stationary member to obtain maximum tractional effort.
Finally, U.S. Pat. No. 4,509,376 shows a dynamometer, used to measure the tension on, speed of, and direction of movement of a hoist rope on a crane. The dynamometer includes a frame comprising three spaced apart blocks coupled to one another by pairs of thin flexible resilient portions. Two pulleys are mounted to the outermost blocks while an offset pulley, coupled to a tension monitoring load cell, is mounted to a central block and presses against the rope. One pulley has three permanent magnets embedded about its periphery, two being axially spaced across from another and the third spaced radially 180 degrees from the others. Sensors mounted to the frame are positioned to sense the passing of the magnets to provide rope speed and direction of travel information in digital form. Tension information from the load cell and speed and direction information from the sensors are supplied to a microprocessor for processing.